The present invention relates to electronic price label (EPL) systems, and more specifically to an EPL including a liquid crystal display (LCD) with a wide vertical viewing angle.
EPL systems typically include a plurality of EPLs for each merchandise item in a store. EPLs include displays which display the price of corresponding merchandise items on store shelves and are typically attached to a rail along the leading edge of the shelves. EPL systems typically obtain their prices from the POS server's PLU file. A store may contain thousands of EPLs to display the prices of the merchandise items. The EPLs are coupled to a central server from where information about the EPLs is typically maintained in an EPL data file. The EPL data file contains EPL identification information, and EPL merchandise item information.
Displays in EPLs are typically liquid crystal displays, due to their low cost. Displays in EPLs are typically not backlit, which means that they must rely on ambient lighting to work. However, most stores use a minimum amount of ambient lighting in order to save cost.
LCDs include optical front and rear polarizers to optimize character display. In known EPLs, the polarizing direction of the front polarizer is horizontal and the polarizing direction of the rear polarizer is vertical. This arrangement provides a wide horizontal viewing angle. However, viewing angles change with changes in ambient lighting, as well as battery voltage and LCD construction.
LCD technology is discussed in U.S. Pat. No. 4,659,181, entitled "Liquid Crystal Displays And Method By Which Improved Apparent Viewing Cones Are Attained Therefor", to Mankedick et al. LCD technology is also discussed in Scientific American article "Working Knowledge, Active-Matrix Liquid-Crystal Displays", by Samuel Mesa, November, 1997, p. 124.
EPLs have traditionally been mounted to shelf edges at a single orientation regardless of shelf height. Since conventional polarizer orientations restrict the vertical viewing angle, a customer is capable of reading EPLs located at eye level, and finds increasing difficulty in reading EPLs on shelves above and below eye level. Variance of customer heights complicates the problem for a retailer.
Therefore, it would be desirable to provide an EPL including an LCD with wide vertical viewing angle to allow a customer to read EPLs at different shelf heights.